1. Technical Field
The present disclosure relates to driving LED (Light-Emitting Diode) lamps and, more specifically, to adaptively dimming the LED lamps.
2. Description of the Related Arts
A wide variety of electronics applications now use LED lamps. These applications include architectural lighting, automotive head and tail lights, backlights for liquid crystal display devices, flashlights, and electronic signs. LED lamps have significant advantages compared to conventional lighting sources, such as incandescent lamps and fluorescent lamps. These advantages include high efficiency, good directionality, color stability, high reliability, long life time, small size, and environmental safety. Accordingly, LED lamps have replaced conventional lighting sources in many applications. For example, LED lamps are often used in applications where the brightness of the light source is adjusted, such as in a dimmable lighting system.
Dimmable lighting systems often use phase cut dimmer switches that employ a triac device to regulate the power delivered to a lamp by conducting during a certain period of an AC voltage supplied to the triac. To maintain the triac in the conducting state, a minimum holding current needs to be supplied to the triac. However, because LED lamp loads vary widely, triac devices may be unable to operate reliably. Furthermore, the minimum holding current varies widely among triac devices, which may further complicate the design of LED-based dimmable lighting systems. When the current through the triac device is less than a minimum holding current threshold, the triac device resets and pre-maturely turns off. As a result, LED lamps may prematurely turn off when they should be on, which may result in a perceivable light flicker or complete failure in the LED lamp.